JPH0419901B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a methanol reforming catalyst. More specifically, in a method for reforming methanol into a gas containing hydrogen and carbon monoxide, the present invention provides a highly active and long-life catalyst that selectively generates hydrogen and carbon monoxide at low temperatures. Methanol can be produced on a large scale from coal, natural gas, etc. via synthesis gas, and is easy to transport, so it is of great interest in the future as an energy source to replace petroleum or as a raw material for various chemical industries. Leaning back. One method of using it is to decompose methanol into a gas containing hydrogen and carbon monoxide, and use this as a pollution-free fuel for automobiles or as a raw material for producing reducing gas. On the other hand, hydrogen can be separated from this cracked gas and used as a fuel for fuel cell power generation and as a hydrogen source for hydrogenation of various organic compounds in the oil refining industry. can be used in the carbonylation process. Thermodynamically, the decomposition reaction of methanol can occur at relatively low temperatures, but the presence of a catalyst is essential in order to carry it out economically. Conventionally, as a catalyst for decomposing methanol, platinum metal elements such as platinum, base metal elements such as copper, nickel, chromium, zinc, and their oxides are supported on a carrier such as alumina (hereinafter referred to as Al ₂ O ₃ ). However, to date, these catalysts still have many problems, such as poor low-temperature activity, lack of heat resistance, and short lifespan. Among the conventional catalysts mentioned above, for example, a catalyst in which platinum is supported on γ-Al ₂ O ₃ is suitable for the following reaction of interest.
In addition to (1), there is a problem in that side reactions such as methane, carbon dioxide, water, ether, aldehyde, etc. are generated, that is, reactions (2) to (5) below are likely to occur. Desired reaction CH ₃ OH→CO+2H ₂ ...(1) Side reaction CH ₃ OH+H ₂ →CH ₄ +H ₂ O ...(2) CH ₃ OH+CO→CH ₄ +CO ₂ ...(3) CH ₃ OH→1/ 2CH ₃ OCH ₃ +1/2H ₂ O ...(4) CH ₃ OH→C+H ₂ +H ₂ O ...(5) Among the above reactions, (1) is the main reaction of methanol decomposition, and the cracked gas generated at this time is This has the advantage that the calorific value of the cracked gas increases by the amount equivalent to the endothermic amount of the decomposition reaction (approximately 22 Kcal/mol), leading to improved thermal efficiency. However, if side reactions like reactions (2) to (5) occur,
Since both of these reactions are exothermic reactions, they are rather a loss in terms of thermal efficiency. Furthermore, when this cracked gas is used as a hydrogen source for various processes, water, ethers, etc. produced as by-products in reactions (2), (4), and (5) become factors that make separation and purification difficult. . Furthermore, among the side reactions, the carbon production reaction (5) causes deterioration of the catalyst or blockage of the reactor, which impedes long-term stable operation. Therefore, in order to solve the above problem, the present inventors solved the above problem by using the following reaction formulas (6) and (7) CH ₃ OH→HCHO+H ₂ →CO+2H ₂ ...(6) CH ₃ OH→1 Focusing on selectively causing dehydrogenation reactions such as /2HCOOCH ₃ +H ₂ →CO+2H ₂ ...(7), we conducted various experimental studies and found that 1 of the group consisting of alumina, titania, zirconia, and silica A catalyst in which noble metals such as platinum and palladium are supported on a carrier consisting of a mixture of oxides of various species, oxides of alkaline earth metal elements, and oxides of rare earth elements has both activity and selectivity in the methanol decomposition reaction. They have found that this is extremely superior, and have completed the present invention. In the method of the present invention, as a catalyst for methanol decomposition,
one of the group consisting of platinum and palladium on a support consisting of a mixture of one or more oxides of the group consisting of alumina, titania, zirconia and silica, oxides of alkaline earth metal elements and oxides of rare earth elements.
The present invention provides a methanol reforming catalyst characterized by supporting more than one type of metal. Here, the carrier consisting of a mixture of one or more oxides of the group consisting of alumina, titania, zirconia, and silica, an oxide of an alkaline earth metal element, and an oxide of a rare earth element is an oxidation of an alkaline earth metal element. A carrier containing at least 1% by weight or more preferably 10 to 98% by weight (based on the total weight of the carrier) of oxides of rare earth metals and oxides of rare earth elements, and as substances other than oxides of alkaline earth metal elements and oxides of rare earth elements. Refers to materials containing alumina, titania, zirconia, silica, and other binder components. As an example, one of MgO, CaO, BaO
More than one species of oxide, La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ ,
One or more oxides of Pr ₆ O ₁₁ and Al ₂ O ₃ ,
There are combinations of one or more oxides of TiO ₂ , ZrO ₂ and SiO ₂ . The preparation method will be explained using the MgO-La ₂ O ₃ -Al ₂ O ₃ carrier as an example: (1) MgO and La ₂ O ₃ powders are mixed with alumina sol. (2) Add an alkali to a mixed solution of an aqueous solution containing an Mg compound and an aqueous solution containing a La-containing compound to form a precipitate.
Mix alumina sol with this. (3) Add an alkali such as soda carbonate to the above mixture and an aqueous solution containing an Al compound to form a precipitate. It can be easily obtained by drying and firing after any of the above steps. Next, the method of supporting the noble metal on the support obtained in this way can be any conventional method without any problem. For example, noble metal nitrate or chloride,
A catalyst on which noble metals are supported can be obtained by immersing the carrier in an aqueous solution of a compound such as an ammine complex, calcining it, and then subjecting it to hydrogen reduction treatment. The supported amount of Pt and Pd (based on the carrier) is preferably in the range of 0.01 to 10% by weight. The catalyst obtained as described above has high selectivity and activity for the reaction of decomposing methanol into gases containing hydrogen and carbon monoxide, and has extremely excellent durability. . Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 Potassium hydroxide aqueous solution was added to a mixed aqueous solution of magnesium nitrate and lanthanum nitrate to form a precipitate, then alumina sol was added and molded, and after drying
The weight ratio of MgO, La ₂ O ₃ and Al ₂ O ₃ is 70:
A 20:10 MgO, La ₂ O ₃ , Al ₂ O ₃ support was obtained. The support thus obtained was immersed in an aqueous solution of tetraammine and platinum dichloride (chemical formula: Pt(NH ₃ ) ₄ Cl ₂ ), dried, and then calcined at 500°C for 3 hours to support 0.5% by weight of platinum. Catalyst 1 was prepared. This catalyst was reduced at 400° C. for 3 hours in a 4% hydrogen stream, and an activity evaluation test was conducted under the conditions shown in Table 1. The results shown in Table 2 were obtained. As a comparison catalyst, conventional γ-Al ₂ O ₃
A catalyst with 0.5% by weight of platinum supported on a carrier was prepared,
Table 2 shows the results of an activity evaluation test conducted at a reaction temperature of 400°C.

【table】

[Table] Note that the methanol reaction rate (%) refers to the ratio of methanol that has undergone a decomposition reaction to the total methanol supplied. Example 2 In the same manner as Catalyst 1 prepared in Example 1, Table 3
A carrier having the composition shown in is prepared, immersed in a chloroplatinic acid aqueous solution, and subjected to hydrogen reduction treatment to reduce the platinum content to 0.3
Catalysts 2 to 6 were prepared, each of which was supported at a weight percent. Regarding these catalysts, an activity evaluation test was conducted under the conditions shown in Table 1 except that the reaction temperature was 400°C.
The results shown in Table 3 were obtained.

[Table] Example 3 CaO prepared using nitrate aqueous solution as starting material
CaO− _CeO2 with _a weight ratio of _CeO2 and _Al2O3 of 70:20:10
-Al ₂ O ₃ carrier with platinum concentration of 0.1, 0.3, 0.5, 1
Catalysts 7 to 10 were supported at a concentration of 0.1 and 0.5% by weight, and catalysts 11 and 12 were supported at a palladium concentration of 0.1 and 0.5% by weight, and further supported at a platinum concentration of 0.3% by weight and a palladium concentration of 0.2% by weight. Catalyst 13 was prepared. Activity evaluation tests were conducted on these catalysts under the same conditions as shown in Table 1, except that the reaction temperature was 400°C, and the results shown in Table 4 were obtained.

[Table] Example 4 A stainless steel reaction tube was filled with 5 c.c. of catalyst 1 prepared in Example 1, and 5 c.c./methanol was added at 400°C.
A durability test was conducted for 800 hours by continuously supplying the material. As a result, it was confirmed that there was almost no change in the methanol reaction rate and cracked gas composition from the initial stage, and that there was no carbon precipitation on the catalyst surface. Example 5 Table 6 prepared using an aqueous solution of chloride as a starting material
Supports 1 to 6 having the compositions shown in are immersed in an acidic solution of dinitrodiammine platinum nitric acid and subjected to hydrogen reduction treatment so that the platinum content becomes 0.5% by weight.
~19 were prepared. Activity evaluation tests were conducted on these catalysts under the conditions shown in Table 5, and the results shown in Table 6 were obtained.

【table】

【table】

[Table] Although the above examples describe granular catalysts, the shape of the catalyst is not particularly limited.
Needless to say, other shapes such as a honeycomb shape may be used. As is clear from the above examples, the methanol reforming catalyst of the present invention has a higher efficiency than the conventional γ-alumina carrier catalyst in the method of reforming methanol into a gas containing hydrogen and carbon monoxide. It is an excellent catalyst that can efficiently and selectively generate hydrogen and carbon monoxide, has high activity at low temperatures, and has a long life.

Claims (1)

[Claims] 1 One or more of the group consisting of platinum and palladium on a support consisting of a mixture of one or more of the oxides of the group consisting of alumina, titania, zirconia and silica, oxides of alkaline earth metal elements and oxides of rare earth elements. A methanol reforming catalyst characterized by supporting a metal.